This invention relates to a method and apparatus for surgically removing a cataractous lens from a human eye. More specifically, this invention is directed to a safe and efficient method and apparatus of small incision, phacoemulsification, irrigation and aspiration of a cataract lens.
Through trauma, age, etc., a human natural crystalline lens may become opaque or cloudy and thus ceases to clearly transmit and focus light. This condition is referred to as a cataract or cataractous lens and is a leading cause of blindness in humans throughout the world.
In the last forty years or so techniques have been developed to surgically remove the cataract lens and replace it with an artificial or intraocular lens.
A cataract lens extraction process may be performed by a number of medically recognized techniques. A well-known and increasingly popular technique among ophthalmic surgeons is known as phacoemulsification, irrigation and aspiration.
Phacoemulsification involves placing two concentric tubes through a corneal incision of approximately three millimeters or so in length made in the region of the limbus where a colored portion of the eye meets a white portion of the eye. The innermost tube is ultrasonically vibrated and this vibrating tip member operably disintegrates the hard nuclear material of the cataract lens after the capsule or skin of the lens has been cut open.
In this type of surgery the vibrating inner tube also functions as an aspirator so that emulsified cataract lens material may be aspirated out of the eye. The outer tube functions as an irrigator allowing for inflow of saline fluid into the eye and preventing the cornea from collapsing as the lens material is being grounded up and aspirated. These concentric tubes at the tip of a handpiece of the system are operably attached to an external source of power, fluid and vacuum which provides for controlled ultrasonic vibration, irrigation and suction.
Once the nucleus of the lens has been ground up and aspirated the handpiece is changed. A new handpiece is used which does not have a vibrating inner tube but the inner tube is still designed to provide for aspiration. This new inner tube usually has a smaller opening at its tip which is rounded off, and usually is either 0.2 or 0.3 millimeters in diameter. This irrigation-aspiration (IA) handpiece is believed to be safer for removal of relatively soft cortical material or cortex which surrounds the hard nucleus of a lens.
It has long been recognized that the two tubes that constitute the handpiece need not be concentric; i.e., that the in-flow tube can be placed through a separate incision from the aspirating and/or vibrating tube. In 1970 the Sparta Corporation manufactured and sold a system with a separate inflow tube and a separate vibrating tube without any source of aspiration. The two tubes were placed through separate incisions and fluid was allowed to flow out around the vibrating tube without any actual aspiration. This system never achieved great popularity or support and is not believed to be currently available.
In the January 1985 issue of "Cataract International Journal of Cataract Surgery", applicant reported initial results of a system of separating an in-flow tube from a vibrating/suction tube and placing the tubes through two separate incisions. This system had the advantage of allowing the cataract to be removed through two small incisions of approximately 1.5 millimeter each. However, since almost all cataract wounds are opened to an incision size of 4 to 6 millimeters to allow for insertion of an intraocular lens this technique also did not gain popularity.
Initially in phacoemulsification the capsule or skin of the cataractous lens is opened at the start of the procedure by making multiple cuts in the skin in what is called often referred to as a "can opener" technique. This technique results in multiple small jagged edges in the anterior surface of the lens capsule. In the late 1980s a new technique for making the opening in the anterior capsule was introduced which has become popular. This technique is called capsulorhexis and involves making a relatively small and circular continuous tear in the anterior capsule which does not leave a jagged edge. Capsulorhexis is believed to exhibit many advantages for an ophthalmic surgeon. However, it has one serious disadvantage. Because the opening in the anterior capsule is relatively small it is difficult to manipulate the concentric tubes of the handpiece so as to remove the cortical material close to where the handpiece has been inserted. In this, if the outermost diameter of an iris is viewed as the face of a clock, then incision of the tip of a phacoemulsification handpiece into the eye is usually made at what is said to be a twelve o'clock position. With a capsulorhexis continuous tear anterior capsulotomy it is difficult to remove the 12:00 o'clock cortical material. Efforts have been made to overcome this problem by bending the tip of the handpiece or using other specialized instruments and techniques; however, none of these have proved to be entirely satisfactory.
The difficulties suggested in the proceeding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness and satisfaction with prior phacoemulsification, irrigation and aspiration method and apparatus appearing in the past. Other noteworthy problems may also exist. Those presented above, however, should be sufficient to demonstrate that phacoemulsification methods and apparatus appearing in the past will admit to worthwhile improvement.